This invention relates to a paper feed device for a printer, for example, provided with both a tractor feed mechanism and a friction feed mechanism serving as paper feed means.
In conventional printers equipped with a tractor feed mechanism and a friction feed mechanism, there is also provided a mechanism for changing the resilient contacting force of a friction roller with a platen in accordance with the mode of paper feed. With this changing mechanism, the friction roller is forced to resiliently contact the platen strongly in a friction feed mode and weakly in a tractor feed mode. For example, Japanese Patent Application No. 60-243323, filed by the present applicant, discloses a mechanism for changing the resilient contacting force of a friction roller with a platen, wherein there is disclosed a cam having a complicated shape, a cam follower, several levers, and a biasing spring.
Such a mechanism is used to control the frictional force between a recording paper and the platen for a tractor feed mode and a friction feed mode. However, this conventional arrangement is complicated in structure, requires a long assembly time, and can hardly set the frictional force between the recording paper and the platen to a proper level in accordance with the mode of paper feed.
Accordingly, it is an object of the present invention to make it easy to set the frictional force between a recording paper and a platen to a proper level for a tractor feed mode and for a friction feed mode using a simplified structure, and to improve the efficiency of assembly.